Starting seeds indoors gives you a head start on the growing season, but timing matters more than anything. Plant too early and your seedlings become leggy and weak. Plant too late and you lose precious growing weeks. Here's how to get it right.

The Golden Rule: Count Back from Your Last Frost Date

Every seed-starting schedule revolves around one date: your last expected frost date. This is the date after which it's generally safe to move tender transplants outdoors. If you don't know yours, our Smart Planting Planner will calculate it from your ZIP code.

From that date, you count backwards. Each crop has an ideal indoor lead time:

8–10 Weeks Before Last Frost

  • Peppers (all types) — slow growers that need the longest head start
  • Eggplant — similar to peppers in timing and warmth needs
  • Onions (from seed) — need time to develop strong root systems

6–8 Weeks Before Last Frost

  • Tomatoes — the classic indoor start; don't rush these
  • Broccoli, cauliflower, cabbage — cool-season crops that transplant well
  • Basil — loves warmth, germinates quickly

4–6 Weeks Before Last Frost

  • Lettuce and greens — fast growers that can also be direct-sown
  • Cucumbers, squash, melons — only if you want a slight head start; they dislike root disturbance
  • Herbs (parsley, cilantro, dill) — moderate lead time

Tips for Indoor Seed Starting Success

  • Use a seed-starting mix, not garden soil — it's lighter and drains better
  • Provide 14–16 hours of light — a south-facing window is rarely enough; use a grow light
  • Keep soil warm — 70–75°F is ideal for most vegetable seeds; a heat mat helps enormously
  • Don't over-water — moist, not soggy; bottom watering prevents damping off
  • Harden off before transplanting — gradually expose seedlings to outdoor conditions over 7–10 days
Starting seeds indoors can save you 50–70% compared to buying transplants — and gives you access to hundreds more varieties than any garden center stocks.

Build Your Seed-Starting Calendar

Want a visual month-by-month schedule tailored to your exact zone? Our Smart Planting Planner generates a full planting calendar showing indoor sowing, transplant, and harvest windows for every crop in your area.

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